Discharge vessel having alpha discharge space which is limited by alpha metal wall



April 17, 1934. J. ALF-[ER 1,955,665

DISCHARGE VESSEL HAVING A DISCHARGE SPACE WHICH IS LIMITED BY A METAL WALL Filed July 1, 1931 Patented Apr. 17, 1934 UNITED STATES PATENT OFFICE DISCHARGE VESSEL HAVING A DISCHARGE SPACE WHICH IS LIMITED BY A METAL WALL burg, Germany Application July 1, 1931, Serial No. 548,179 In Germany July 3, 1930 2 Claims.

In discharge tubes, in particular in those of the type operating with a pure electron discharge, often undesired stresses of the glass wall occur in the proximity of the electrodes. These loads exert on the one hand an unfavourable influence on the discharge and on the other they are likely to cause puncturing of the glass wall especially when the outer side of this wall contacts with bodies having earth potential. It has already been proposed to prevent such stresses by providing screens within the tube or by providing a metal cylinder within the tube which cylinder is arranged concentrically with respect to the glass wall and which is connected to an analogous metallic cylinder provided on the outer wall of the discharge vessel, said connection being established by hermetically sealing a metal wire through the glass wall.

The present invention has for its purpose to improve the construction above referred to. At the edges of these metal cylinders which are opposite each other relatively high intensities of field occur, by which the puncturing of the glass wall is furthered at these points. In order to avoid these high intensities of field, the inner metal cylinder according to the invention is placed in such a manner, that it extends at least on one side beyond the edge of the outer metal cylinder.

By so forming the metal cylinder so as to protect the glass wall, the density of the electric lines of force going from the electrodes to the edges of the outer cylinder, is materially reduced, so that the glass wall is no longer exposed to dangerous electric stresses.

The accompanying drawing shows by way of example an X-ray tube having a cylindrical glass wall 1. A metal cylinder 4 surrounds the cathode 2 and the anode 3 on the outer side of the glass wall 1. Opposite this cylinder is placed a metal cylinder 5 which is provided on the inner side of the glass wall. The metal cylinder 5 extends on both sides beyond the outer metal cylinder 4 and is electrically connected to the latter by means of a wire 6 sealed through the glass wall 1. Both metal cylinders are provided with a window '7 through which the rays may emerge from the X-ray tube.

What I claim is:

1. A discharge tube of the character described comprising a cylindrical glass envelope of substantially uniform diameter from end to end, a cathode and an anode arranged in spaced relation in said envelope, a cylindrical conducting sleeve member on the outside surface of said envelope midway between the ends thereof and surrounding the operative parts of said cathode and anode, a second conducting sleeve member on the inside of said envelope surrounding the operative parts of saidcathode and anode and extending on at least one side beyond the firstmentioned sleeve member and a conductive connection between said sleeve members.

2. An X-ray tube comprising a substantially cylindrical glass envelope, a cathode and an anode in said envelope, a metallic sleeve on the outside of said envelope surrounding said cathode and anode, a second metallic sleeve on the inside of said envelope surrounding said cathode and anode and extending axially of the tube beyond the ends of the first-mentioned sleeve and a conductive connection between said sleeves.

J OSEF ALFTER. 

